Sewing machine drive with position control means and rotational speed measuring generator

ABSTRACT

A control assembly for a sewing machine comprising a rotational speed measuring generator and a position control means which form an assembly unit mounted on a shaft portion, which rotates with the driven shaft of the machine, where the rotor of the generator which is a multipole magnet, the stator and the position control means occupy very little space, and where the stationary parts are mounted on a common support which is movable or adjustable relative to the rotating parts.

United States Patent [72] Inventor Alfred l-leidt [56] References Cited schwellinzen, Baden, Germany UNITED STATES PATENTS [211 P 7681725 2,920,221 1/1960 Schwab 1 12/219(A x [22] Flled Oct. 18,1968 1451 Patented Feb. 16,1971 FOREIGN PATENTS [73] Assignee Frank] 8; Kirchner, Fabrik fur 930,019 7/1963 Great Britain 1 12/219(A) Eleklromofioren und eleklfischg Apparale 1,475,522 2/1967 France 1 12/219(A) I Schweuing'n Baden Germany Primary Examiner-Alfred R. Guest [32] pmmy 1968 Attorney-Robert H. Jacob [33] Germany [31] 1,760,008

ABSTRACT: A control assembly for a sewing machine com- [54] prising a rotational speed measuring generator and a position MEASURING GENERATOR control means which form an assembly unit mounted on a shaft portion, which rotates with the driven shaft of the 9 Clams 7 Drawing machine, where the rotor of the generatorwhich is a multipole [52] [1.8. CI. 112/219 magnet, the stator and the position control means occupy very [51] Int. Cl..... D05b 69/22 little space, and where the stationary parts are mounted on a Field of Search 112/219, common support which is movable or adjustable relative to 219 (A) (cursory), 220

the rotating parts.

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PATENTED FEB 1 6 I87! lnvenfar:

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Inventor.- Alf ff D Hf/DT MEANS AND ROTATIONAL SPEED MEASURING GENERATOR BACKGROUND OF TI-IEVINVENTION The present invention relates to sewing machines and means for controlling needle movements and also determining the rotational speed 'of the machine. Drives for sewing machines are known which are required to stop the machine in a predetermined position in which the needle of the sewing machine is, for example, either in its lowest or in its highest position. In order to accomplish the accurate stopping of the machine in the desired position, the speed of the driven part is automatically reduced with these drives before the stopping action takes place. As an indicating device for the position to be reached the machines utilize contact or signalling devices coupled to and rotating with the shaft of the machine or with the drive means, which are generally referred to as position control means. Furthermore, for checking or controlling the speed of the machine, speed-measuring generators or tachometer generators are known. An arrangement with which the control device in accordance with the present invention may be utilized is disclosed in US. Pat. No. 3,407,910 issued in the name of the Applicant.

SUMMARY OF THE INVENTION The invention relates to sewing machine drives of the type having a position control means and a speed-measuring generator which continuously checks the speed and includes the feature that this generator is provided on the'balance wheel shaft of the sewing machine. To be sure, it is not especially desirable to lengthen the balance wheel shaft carrying the position control means by mounting additional components thereon. However, the invention takesadvantage of Owing to the small space requirement the speed-measuring generator can readily be combined with the position control means in a structural unit.

It is'also possible to combine the generator with the balance wheel of the sewing machine to constitute a structural unit. In accordance with the invention, the construction of the generator in the form of a disc of negligible axial length is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will become apparent from the following specification with reference to the accompanying drawings in which:

FIG. I is a simplified view of a sewing machine provided with a position control means and a speed-measuring generato FIG. 2 illustrates the position'control means and generator in a vertical section as a structural unit including the control head;

FIG. 3 is anend view of the control head taken from the right side of FIG. 2 with the housing removed;

FIG. 4 is a view of the control head taken from the left side of FIG. 2;

FIG. 5 is a section along the line C-D in FIG. 3;

FIG. 6 is a partial sectional view of the pole wheel of the generator in the same plane as the section in FIG. 2, but to an enlarged scale, and I FIG. 7 is a view of the pole wheel of the generator taken in axial direction. a r

2. A DESCRIPTION OF THE INVENTION The sewing machine A is shown in FIG. lmerely in outline. The shaft B carriers the balance wheel C, and externally thereof at the end of shaft B the position control means D and the speed measuring generator E. The schematic illustration is merely intended to indicate the basic arrangement regardless of the actual dimensions.

In the embodiment in accordance with- FIG. 2 and the following illustrations, the generator is not located outside the position control means but between the same and the shaft end of the sewing machine alongside the balance wheel. I

The control head illustrated in FIG. 2' constitutes a closed structural unit which can be readily mounted on different types of sewing machines without requiring changes in the machine per se. This unit is carried by a shaft 2 which is constructed in the form of a socket l at the end which faces the sewing machine and which defines the driven portion of the unit. This socket is mounted on the end of the sewing machine shaft (not shown) alongside the balance wheel and is secured thereto by means of three screws in a manner that the shaft 2 of the control head constitutes a rigid extension of the sewing machine shaft. A support plate 4 which carries all other parts of the control head is supported on shaft 2 by means of a double-race ball bearing 7 disposed around the shaft.

supporting plate 4. A circular cord ring 8 seated in an annular groove of the bore for the ball bearing clamps or wedges the outer ring of the ball bearing 7 in the supporting plate 4 and prevents the outer ring from being carried along in the ball bearing by the friction of the balls. The circular cord ring 8, however, permits sliding of the ball bearing 7 into the bearing bore of the plate 4 with sliding' fit or pinch fit and thusprovides for easy assembly. The bearing plate 4 can be pressed from glass fiber reinforced plastic material. Axial securement of the ball bearing 7 is provided by the pressure plate 9 and the screws 10 which fix it in position.

The generator pole wheel 11- as well as the control discs 12 and 13 of the position control means are disposed on the bearing or supporting shaft 2. The generator pole wheel II "is retained on the supporting shaft 2 with a pinch fit. The outer end of the shaft 2 has a thread 2'. The control disc l2is clamped in position between a fastening nut 14 threadedly received on thread 2' and a spacingsleeve l5 fitted on the supporting shaft. The control disc 13 is held in position on. the supporting shaft by two securing nuts 16 and 17. By virtue of this arrangement the two controldiscs can be adjusted to different angular positions independently from one another. As described more in detail hereinafter, the control discs have radial slots. Therefore, it is possible to pull themoff in a radial direction from the shaft2 after loosening the respective nut 14 or 17. In order to make possible exact centering of the control discs they are seated on the centric projections of nuts 14 and 16.

The control discs may be contact diaphragms or also optical or magnet shutter blades with slots. In the embodiment described the discs are assumed tobe slotted magnet shutter blades with radially extending slots-The shutter blades or diaphragms are disposed between several coils I2, 13 and 13" which are to be coupled magnetically with one another. Due to their magnetic shielding effect they weaken the coupling field practically to zero while the blade slot does not enter between the coils. However, the slot allows the coupling The generator is accommodated in the control head between ball bearing 7 and the position control means. The generator is a multiple pole AC generator of the claw pole type known per se and comprises the pole wheel mounted on the shaft 2 and a wound stator 22 which occupies only a sector of the circumference and into the winding 22' of which a current of relatively high frequency is induced by the rotating pole wheel. The arrangement of the generator proximate the ball bearing 7 results on the one hand in a favorable distribution of weight and, on the other'hand, it leaves the control discs free so that they can be adjusted as required.

The stationary part 18 of the control head is secured to the support plate 4 by means of screws 19. On its side which rests on the support plate 4 it has a lug 20 that engages grooves 21 in the support plate 4. This guide means affords the possibility of displacing the stationary part of the control head in upright position when the airgap is to be adjusted between the generator pole wheel 11 and the stator 22. The slots 19' in the part 18 of the control head through-which the screws 19 extend serve for the same purpose. The supply cord 23 engages the support plate 4 by means of a break resisting sleeve 24 and is retained by a pull-absorbing sleeve 25. The individual leads are connected to the solder contacts of a connection strip 26. This connection strip is secured by hollow rivets 26' to the bottom of the control head portion 18.

A multiple pole plug 27 connects the position indicator with the control box of the sewing machine. The housing or cover 28 may be pressure cast zinc and is secured by means of screws 29 onto the support plate 4.-

The generator pole wheel is illustrated in FIGS. 6 and 7 as it is press-fitted onto the bearing shaft 2 in accordance with the invention. A permanent magnet 31 of annular shape which is magnetized in the direction of the axis of the annulus serves for energizing the pole wheel. It is radially encompassed by the claw shaped poles of two stellar shaped pole wheel halves 32, 32 which are angularly displaced relative to one another. After inserting a circular cord 34 which encompasses the annular magnet 31 all elements are held on the bearing hub 33 by the borders or collars 35.

This manner of construction makes it possible to accurately center the permanent magnet in simple and protective fashion and thus avoid any undesirable eccentricity. Force fitting the permanent magnet 31 onto the bearing hub 33 would not be suitable owing to its tendency to break. Gluing the permanent magnet 31 onto the hub 33-would be very costly and cumbersome, because this would involve exact centering of the magnet with respect to the hub. 7

All structural requisites mentioned are met by the use of the circular cord ring 34 which compensates by means of its elastically for the considerable tolerance of the outer diameter and simultaneously compels it to be centered in the pole wheel halves 32. Furthermore the considerable tolerance of the inner diameter of the magnet ring 31 is made harmless, because a sufficiently large airgap can remain between the inner bore of the permanent magnet 31 and the outer circumference of the bearing hub 33.

The stator 22 of the generator and the stationary components of the position control means are carried in a common support 18, which as mentioned above, is displaceable in a guide groove 21 on the support plate 4 and can be clamped in its adjusted position on the plate 4 'means of screws 19. The

support 18 is provided with recesses in which the components that are mounted on its are seated. These may be covered by casting resin and thereby held inaccurate positions while protected against shocks and moisture. Any special mounting or retaining means are not needed so that also in this respect a space-saving arrangement is achieved.

Having now described my invention with reference to the embodiment illustrated in the drawings,what I desire to protect by Letters Patent of the UnitedStates is set forth in the appended claims.

I aim:

lf Control device for sewing machinein the form of a structural assembly unit comprising a position control means and a rotational speed-measuring generator for continuously checking the speed of the sewing machine, said unit having a driven portion adapted to be driven by the balance wheel shaft of a sewing machine and said generator comprising a rotor in the form of a wheel mounted concentric with said driven portion and a stator disposed in inductive relationship proximate said rotor.

2. Control device for sewing machine in accordance with claim 1, where said speed-measuring generator is in the form of a disc having relatively short axial length.

3. Control device in accordance with claim 1, where said driven portion is a shaft having coupling means adapted to releasably engage the balance wheel shaft of a sewing machine.

4. Control device in accordance with claim 3 where said shaft having said coupling means supports said rotor and at least one control disc of said position control means.

5. Control device in accordance with claim 2, where said generator is a multiple pole AC generator comprising a pole wheel and said stator, said stator being an induced element extending about a small sector of said wheel and having fewer poles than said pole wheel.

6. Control device in accordance-with claim 1, including a shaft portion having a connecting socket adapted to be mounted on the shaft of the machine, said shaft portion carrying a ball bearing proximate said socket, said rotor adjacent said ball bearing and at least one control disc of said position control means.

7. Control device in accordance with claim 6, including a supporting plate disposed around said ball bearing, said supporting platehaving secured thereto said stator portion of said generator.

8. Control device in accordance with claim 7, including interengaging means between said stator and said supporting plate and releasable fastening means permitting adjusting movement of said stator radially with respect to said shaft portion.

9. Control device in accordance with claim 6 including a common support carrying said stator comprising the stator magnet of said generator and stationary components associated with said position control means, said supporting plate presenting guide means and said common support having a lug or the like received in said guide means, and mounting screw means extending between said plate and said common support retaining said common support on said plate and upon release permitting adjustment of said stator portion relative to said rotor. 

1. Control device for sewing machine in the form of a structural assembly unit comprising a position control means and a rotational speed-measuring generator for continuously checking the speed of the sewing machine, said unit having a driven portion adapted to be driven by the balance wheel shaft of a sewing machine and said generator comprising a rotor in the form of a wheel mounted concentric with said driven portion and a stator disposed in inductive relationship proximate said rotor.
 2. Control device for sewing machine in accordance with claim 1, where said speed-measuring generator is in the form of a disc having relatively short axial length.
 3. Control device in accordance with claim 1, where said driven portion is a shaft having coupling means adapted to releasably engage the balance wheel shaft of a sewing machine.
 4. Control device in accordance with claim 3 where said shaft having said coupling means supports said rotor and at least one control disc of said position control means.
 5. Control device in accordance with claim 2, where said generator is a multiple pole AC generator comprising a pole wheel and said stator, said stator being an induced element extending about a small sector of said wheel and having fewer poles than said pole wheel.
 6. Control device in accordance with claim 1, including a shaft portion having a connecting socket adapted to be mounted on the shaft of the machine, said shaft portion carrying a ball bearing proximate said socket, said rotor adjacent said ball bearing and at least one control disc of said position control means.
 7. Control device in accordance with claim 6, including a supporting plate disposed around said ball bearing, said supporting plate having secured thereto said stator portion of said generator.
 8. Control device in accordance with claim 7, including interengaging means between said stator and said supporting plate and releasable fastening means permitting adjusting movement of said stator radially with respect to said shaft portion.
 9. Control device in accordance with claim 6 including a common support carrying said stator comprising the stator magnet of said generator and stationary components associated with said position control means, said supporting plate presenting guide means and said common support having a lug or the like received in said guide means, and mounting screw means extending between said plate and said common support retaining said common support on said plate and upon release permitting adjustment of said stator portion relative to said rotor. 